Controlled and Assisted Cloning of an Arbitrary Unknown States via Maximal Slice States

The purpose of this article is to further investigate the assisted cloning of an arbitrary unknown state via maximal slice states under the control of the supervisor. By making use of three-qubit maximal slice states and appropriate measurement basis, we propose efficient controlled schemes for cloning arbitrary unknown multi-qubit states with assistance from a state preparer. The first stage of schemes requires usual teleportation and proper measurement basis chosen by controller, and in the second stage the state preparer disentangles the left over entangled states by introducing auxiliary particles, implementing controlled NOT gates and two special projective measurements, and communicates some classical bits to the sender of the first stage, so that perfect copies are produced. Based on the implementation schemes for copying arbitrary unknown single- and two-qubit states, we have derived the controlled and assisted cloning protocols for arbitrary unknown multi-qubit states.